Polysilazane compounds can be generally converted into siliceous substances by heating. However, if normal polysilazane compounds are simply used, they have many problems that should be improved. For example, the conversion into the siliceous substances proceeds very slowly and needs high temperature. Since there is thus large room for improvement, various studies and researches have been made to overcome the problems.
In order to improve the above problems, it is proposed to modify the polysilazane compounds themselves or to incorporate particular additives into compositions containing polysilazane compounds. For example, an N-heterocyclic compound (described in, for example, Patent document 1), an alkanol amine (described in, for example, Patent document 2) or an amine and/or acid (described in, for example, Patent document 3) is added as the additive into a polysilazane-containing composition so that the composition can form a siliceous film at a low temperature. The amine compounds described as the additives in the above documents are also used in a composition containing a diamine compound for other purposes such as reducing film-roughness or avoiding coating-unevenness (described in, for example, Patent documents 4 and 5), and further they are still also used in a composition containing a polyamine compound for the purpose of hardening epoxy resin (described in, for example, Patent document 6).
Lately, applications of siliceous films formed from polysilazane-containing compositions have been expanding. In accordance with that, various processing methods thereof have been researched. For example, a method is developed that comprises the steps of: forming a siliceous coating layer on a substrate, forming another layer thereon to overlap the coating layer, and subjecting the overlapping layer to secondary processing. If a conventional polysilazane-containing composition is employed in this method, the conversion reaction proceeds rapidly and almost finishes before the overlapping layer is formed thereon. Consequently, when once the overlapping layer is formed, it is often difficult to carry out various secondary processing treatments for forming a dense siliceous film from the coating layer. On the other hand, however, if the polysilazane composition is completely prevented from undergoing the conversion reaction in view of the secondary processing, the surface of the composition spread on the substrate is not cured and hence the coating layer of the composition cannot be fixed on the substrate. As a result, the substrate coated with the composition is difficult to handle in practice. For example, if a resin film is adopted as the substrate, it is impossible to wind up the resin-film substrate coated with the polysilazane composition.
In consideration of the above, it is desired for the conversion reaction of the polysilazane composition not to finish completely but to proceed to such a degree that the surface of the composition layer can be dried enough to keep the layer fixed on the substrate. However, conventional polysilazane compositions are produced with the aim of making the conversion reaction proceed as completely as possible, and accordingly the conversion reaction cannot be kept unfinished for a certain period.